Amy Williams of RNZ A parent of a teenager who eats only plain foods including bread, crackers and pasta says it is terrifying to learn such restrictive diets can cause permanent vision loss. It follows two eye specialists' warning there were children in New Zealand who had gone blind due to malnutrition. Sarah and her husband have tried everything to get their son, whose eyesight is good, to eat a balanced diet. "He is a very plain beige food eater and he's been like that from a very young age." She said her son will eat only plain foods such as bread, crackers, chips, pasta and brown rice. "It's really hard. You can get angry, you can get sad, grumpy, you know we've tried every which way to get him to eat." When he was diagnosed with autism, and later avoidant restrictive intake disorder, it came with some relief but Sarah said the worry remained about his health. Her son had regular check-ups, saw a paediatrician and took a nutrient drink three times a day alongside vitamin supplements.…